Technical Field
The disclosure relates to a printing apparatus, and more particularly to a three-dimensional (3-D) printing apparatus and an inkjet coloring method thereof.
Description of Related Art
With the advance in computer-aided manufacturing (CAM), the manufacturing industry has developed a three-dimensional (3-D) printing technology to rapidly convert original design concept into physical objects. The 3-D printing technology is actually a general designation of a series of rapid prototyping (RP) techniques. A basic principle thereof is an additive manufacturing by using a RP machine to form a sectional shape of a workpiece in an X-Y plane through scanning and to intermittently shift by a layer thickness along a Z-axis, so as to finally form a 3-D object. The 3-D printing technology is not limited to any geometric shape, and the more complex the components are, the more excellent the RP technology can demonstrate. The 3-D printing technology may greatly save manpower and processing time. With a demand of shortest time, a digital 3-D model designed by using a 3-D computer-aided design (CAD) software may be truthfully presented as touchable.
Taking a fused deposition modeling (FDM) as an example, a building material is made into wires thereby, and then the building material after being heated and melted is stacked layer by layer on a forming platform according to the desired shape/contour, so as to form a 3-D object. Therefore, in the conventional color FDM 3-D printing method, the exterior is usually colored after the 3-D object is completed, or the 3-D object is manufactured by using a colored forming material. In the former case, however, the color ink is only applied to the outer surface of the 3-D object which may be slightly inferior in color properties and variability. On the other hand, in the latter case, the forming wire materials in different colors has to be repeatedly changed and used in order to achieve a multiple-color effect, which results in unsatisfactory efficiency in manufacturing a colored three-dimensional object. Thus, a method of printing a colored 3-D object is recently provided, in which layer objects for forming a 3-D object are colored layer by layer using an inkjet mechanism in the process of manufacturing the 3-D object. However, if a thickness of each layer object is large, the layer object cannot be entirely dyed by the color ink, such that unexpected stripes may occur to the appearance of the 3-D object due to the incompletely dyed layer objects. Accordingly, how to improve the aforementioned issues has become one of the subjects that the technicians have to consider.